He went on to accuse City - and Paris Saint-Germain - of cheating.
When the initial deal was signed in October 2015, both Guardiola and City made no public comment on the agreement. "All I know is that we are not the only club to spend a lot of money, if you want to achieve another level that is what you have to do".
The leaked documents appear to show that tens of millions of pounds that were supposed to have come from City's sponsors Etihad Airways was paid directly to the club by the owners.
A big chunk of City's support make their feelings about UEFA known at every European night, stemming back to the fine and sanctions dished out against the club for breaching the FFP rules in 2014.
La Liga president Javier Tebas has long spoken out against Manchester City and PSG describing their conduct as financial doping and La Liga spokesman Joris Evers told Reuters and the BBC the time for action is needed. Of course we want to follow the rules.
La Liga, the Spanish top flight, has said that, if UEFA does not act, it will "launch a complaint with European Union competition authorities".
Der Spiegel is planning to publish further stories related to City on Wednesday and Thursday. One memo from chief executive Ferran Soriano is said to have read, "We will need to fight this and do it in a way that is not visible, or we will be pointed out as the global enemies of football".
The magazine said the name "Longbow" was chosen, according to City's chief legal adviser, Simon Cliff, as it was "the weapon the English used to beat the French at Crecy and Agincourt" in the Hundred Years' War.
That included selling players' image rights to an external company, therefore writing off that cost from their accounts.
The accusation from Der Spiegel after viewing internal documents is that it was Sheikh Mansour's company, Abu Dhabi United Group, that gave the Rowlands the money "for the purchase of the marketing rights and to pay the players for their marketing appearances".
That is the incredibly damning assessment of Manchester City from German magazine Der Spiegel in the second instalment of the unmasking of the Premier League champions this week.
They spoke also of an "organised and clear" attempt to damage their reputation.
Der Spiegel calls the settlements "weak" and claims Uefa "wasn't even entirely aware of the degree to which it had been deceived".
Documents also suggested that Abu Dhabi United Group had invested more than £1.1bn in 2012, four years after Sheikh Mansour took over the club.
Der Spiegel said this helped turn nearly 30 million euros ($34 million) into revenue instead of a cost, for the goal of UEFA's investigation of club accounts.
Since 2008, City have won three Premier Leagues, an FA Cup and three League Cups, and have spent more than £1.4bn on players.